問題文
A data source tests the connections it hands out, and the administrator wants the cost of that testing brought down. What does the span for trusting an idle pooled connection do, and what may become of the pool where one thread of a test hangs?
選択肢
- It lets the test be skipped where the request comes in within that span of the connection having been tested or used with success, and the pool may declare the database out of reach, put itself out of use and kill every connection it holds, reserved or not, once one thread of a test has hung too long
- It lets the test be skipped where the request comes in within that span of the connection having been tested or used with success, and the pool may leave the hung thread where it stands and carry on handing out the connections it holds, since one test that never returns counts as a single failure
- It lets the test be run a second time within that span so that a connection used with success is proven afresh, and the pool may declare the database out of reach, put itself out of use and kill every connection it holds, reserved or not, once one thread of a test has hung too long
- It lets the test be run a second time within that span so that a connection used with success is proven afresh, and the pool may hand the hung thread over to another data source of the domain, since a test that never returns is counted against whichever data source holds the table it reads